docs: def command(self, command, value=1, callback=None,
                  check=True, allowable_errors=[], **kwargs):
          """Issue a MongoDB command.
  
          Send command `command` to the database and return the
          response. If `command` is an instance of :class:`basestring`
          then the command {`command`: `value`} will be sent. Otherwise,
          `command` must be an instance of :class:`dict` and will be
          sent as is.
  
          Any additional keyword arguments will be added to the final
          command document before it is sent.
  
          For example, a command like ``{buildinfo: 1}`` can be sent
          using:
  
          >>> db.command("buildinfo")
  
          For a command where the value matters, like ``{collstats:
          collection_name}`` we can do:
  
          >>> db.command("collstats", collection_name)
  
          For commands that take additional arguments we can use
          kwargs. So ``{filemd5: object_id, root: file_root}`` becomes:
  
          >>> db.command("filemd5", object_id, root=file_root)
  
          :Parameters:
            - `command`: document representing the command to be issued,
              or the name of the command (for simple commands only).
  
              .. note:: the order of keys in the `command` document is
                 significant (the "verb" must come first), so commands
                 which require multiple keys (e.g. `findandmodify`)
                 should use an instance of :class:`~bson.son.SON` or
                 a string and kwargs instead of a Python `dict`.
  
            - `value` (optional): value to use for the command verb when
              `command` is passed as a string
            - `**kwargs` (optional): additional keyword arguments will
              be added to the command document before it is sent
  
          .. mongodoc:: commands
          """
  
          if isinstance(command, basestring):
              command = SON([(command, value)])
  
          command.update(kwargs)
  
          self.connection("$cmd").find_one(command,callback=callback,
                                         _must_use_master=True,
                                         _is_command=True)